Field of the Invention
The invention relates to a turning or reversing device for a real or flat sheet-like material, which is printable on both sides thereof, with a storage device for the sheet-like material to be turned, which is assigned to the turning device.
The published German Patent Document DE 41 40 762 A1 is concerned with a sheet guiding device which may be used selectively in recto and verso printing mode, a respective sheet being turnable by this device, during recto and verso printing, in accordance with the principle of sheet trailing-edge turning, and pneumatically operating and mechanical devices are provided under the impression cylinder preceding the turning drum. In order to provide a sheet guiding device by which the sheet can be guided and led in a smudge-free manner in the turning or reversing phase, without formation of a sheet wad, the impression cylinder has assigned thereto, at an angle of inclination xcex2, a guide doctor blade capable of being acted upon pneumatically and provided with individual air outlet orifices. After impression cylinder grippers have opened, the printed sheet is released from the printing surface of the cylinder by blowing or blast air, steered under the guide plate and both held up and transported in the direction of the transfer cylinder by the emerging blowing air, until the turning drum conveys the sheet farther on.
The published German Patent Document DE 44 24 967 C2 is concerned with a method and a device for sheet turning or reversing. What is proposed is a method for sheet turning based upon the principle of trailing edge turning in sheet-fed rotary printing machines capable of being converted from recto printing to recto and verso printing mode, in which method, in recto and verso printing, a print carrier sheet guided on a cylinder is gripped at the trailing edge thereof by a pivotable sheet take-over system of a turning drum following or located downline from the cylinder, at the tangent point of the turning drum and the cylinder, and is transported further. At the tangent point, the start of the sheet carrier sheet is released by the sheet gripper of the cylinder and, immediately after or downline from the tangent point, is guided on a path deviating from the surfaces of the cylinder under the turning drum.
Storage of sheet-like material on the impression cylinders of a rotary printing machine requires free space below the impression cylinder, so that the sheet-like material can be received over the entire length thereof. Thus, the sheet can be gripped and turned by the turning drum without coming into contact with machine parts, casings of transfer drums, guide plates or other sheets. The requirement for storage space is contradictory or opposed to the requirement that the sheet-like material should be printed out during the transfer in recto printing mode to the transfer drum following the impression cylinder. If the sheet-like material is intended to have already left the printing nip during transfer in recto printing, it is necessary, in printing units with a single-drum turning device, to provide in each case a complete length of the maximum processable printing format as a freely available sheet transport stage both between the transmission cylinder and the gripper median line to a following or downline transfer drum and between the following or downline transfer drum and the transfer median line to the preceding or upline transfer drum, taking into account the collision space of the fittings provided thereat. Furthermore, it is also necessary to take into account the necessary space requirement for accessibility and for the fittings in front of or upline from the printing nip.
A further possibility for solving the depicted technical problem is to pivot the arrangement of cylinders to an extent that the construction space for printing out and storage is gained at the expense of the fittings in front of or upline from the printing nip. This measure, however, is detrimental to the quality of sheet guidance in front of or upline from the printing nip, so that the print quality which is attained decreases. Moreover, serious effects on the accessibility of the fittings are to be feared. This makes it difficult to clean, perform settings and conduct servicing during maintenance work.
A further possibility for a remedy is to restrict the permissible print carriers for the recto and verso printing mode to those print carriers which remain adhering to the circumference of the impression cylinder and which do not move away from the impression cylinder due to the influence of gravity and to flexural rigidity. By this measure, the collision space to be kept free could be restricted and the permissible format length could be enlarged. However, the restriction to only some permissible print carriers for rotary printing machines with turning devices is seriously detrimental to the processable print carriers and can only be a compromise solution.
In view of the developments in the prior art, which have been outlined, and the technical problem, which has been described, it is an object of the invention to provide a turning or reversing device with a storage device for flat sheet-like material wherein the storable sheet length is maximized during the turning or reversing of the sheet-like material.
With the foregoing and other objects in view, there is provided, in accordance with a first aspect of the invention, in combination, a device for turning sheet-like material, with an impression cylinder for guiding the sheet-like material, the impression cylinder being preceded by a first transfer cylinder and followed by a second transfer cylinder, the sheet-like material being receivable on an outer jacket surface of the impression cylinder so as to be printable by a third transfer cylinder, comprising a storage device, and a device for imparting a deformation in the sheet-like material during entry thereof into the storage device and while the sheet-like material is gripped at an edge thereof.
In accordance with another feature of the invention, the storage device extends below the impression cylinder and the first and the second transfer cylinders.
In accordance with a further feature of the invention, the storage device has a contour for guiding a print carrier, the contour corresponding to a wedge-shaped region between two of the cylinders which are mutually cooperating.
In accordance with an added feature of the invention, the storage device has, below the impression cylinder, a nip width narrowing continuously in a direction of entry of the sheet-like material.
In accordance with an additional feature of the invention, the storage device has a run-on slope in a wedge-shaped region of the nip.
In accordance with yet another feature of the invention, the combination includes a retaining element arranged at the storage device in an upper region thereof, below a transfer median line, for retaining in the storage device the sheet-like material which has entered the storage device.
In accordance with yet a further feature of the invention, the retaining element has perforations formed therein like comb tines for allowing passage therethrough of holding elements of the impression cylinder for gripping the sheet-like material.
In accordance with yet an added feature of the invention, at least one coating is provided on the retaining element for damping impacts of the sheet-like material.
In accordance with yet an additional feature of the invention, the combination includes an encapsulated damping gel provided on the retaining element.
In accordance with still another feature of the invention, the combination includes cyclically activatable blowing nozzles provided on the impression cylinder for ejecting the sheet-like material into the retaining element.
In accordance with still a further feature of the invention, the combination includes cyclically activatable ejector pins provided on the impression cylinder for ejecting the sheet-like material into said retaining element.
In accordance with still an added feature of the invention, the combination includes free jet devices actable free of contact on a side of the sheet-like material yet to be printed, for imparting a deformation in the sheet-like material for maximizing the storable length thereof.
In accordance with still an additional feature of the invention, the combination includes a blast device for discharging free jets, the blast device being received in a gap formed in the impression cylinder.
In accordance with another feature of the invention, the combination includes gripping devices of the transfer cylinder following the impression cylinder, the gripping devices serving for fixing the sheet-like material at one edge during entry of the sheet-like material into a storage device.
In accordance with a further feature of the invention, the gripping devices are pivotable about an axis thereof for imparting to the sheet-like material a bending moment for deforming the sheet-like material.
In accordance with an added feature of the invention, the gripping devices serve for executing a yielding movement retreating behind a path of an edge of the sheet-like material, within an enveloping curve of the transfer cylinder following the impression cylinder.
In accordance with an additional feature of the invention, a change in distance between a gripper path of the gripping devices and an outer jacket surface of the transfer cylinder following the impression cylinder is variable during rotation of the impression cylinder and the transfer cylinder following the impression cylinder for guiding a print carrier.
In accordance with another aspect of the invention, there is provided a printing unit with a device for turning sheet-like material, and including an impression cylinder for guiding the sheet-like material, the impression cylinder being preceded by a first transfer cylinder and followed by a second transfer cylinder, the sheet-like material being receivable on an outer jacket surface of the impression cylinder so as to be printable by a third transfer cylinder, comprising a storage device, and a device for imparting a deformation in the sheet-like material during entry thereof into the storage device and while the sheet-like material is gripped at an edge thereof.
In accordance with a concomitant aspect of the invention, ther is provided a multicolor rotary printing machine with a device for turning sheet-like material from a printed side onto a side yet to be printed, and including an impression cylinder for guiding the sheet-like material, the impression cylinder being preceded by a first transfer cylinder and followed by a second transfer cylinder, the sheet-like material being receivable on an outer jacket surface of the impression cylinder so as to be printable by a third transfer cylinder, comprising a storage device, and a device for imparting a deformation in the sheet-like material during entry thereof into the storage device and while the sheet-like material is gripped at an edge thereof.
The advantages of the construction proposed in accordance with the invention are, above all, that the print carrier, whether paper or cardboard, is deformed out of position around the impression cylinder after a take-over of an edge of the sheet-like material by the grippers of a transfer cylinder following or downline from the impression cylinder. The deformation of the sheet-like material achieves a better utilization of the storable sheet length, in that, in this regard, the sheet-like material can be curved so that even a wedge-shaped region below a transfer median line between two mutually cooperating cylinders guiding a print carrier can be utilized as storage space. The storage device which, according to the invention, projects into the wedge-shaped region of two mutually cooperating cylinders guiding sheet-like material, is configured so that the surface thereof is at a maximum and can therefore store even the maximum processable format.
In an advantageous development of the idea upon which the invention is based, the storage device extends over the entire printing unit length below the cylinders guiding the sheet-like material. Thus, a continuous surface can be formed below the cylinders guiding the sheet-like material, so that an integral or one-piece construction of the storage device configured in accordance with the invention can be produced advantageously in terms of manufacturing technology.
The storage device has a contour corresponding to the wedge-shaped region of two mutually cooperating cylinders and therefore has an at least approximately triangular configuration in the upper region thereof extending into the wedge-shaped region. This configuration ensures the use of the continuously narrowing cylinder wedge in a direction towards the transfer median line of the impression cylinder and the preceding transfer cylinder. The end point of the storage device configured in accordance with the invention is determined by the maximum processable sheet format to be turned, which must be received in a curved position by the storage device.
The storage device below the impression cylinder has a nip profile narrowing continuously in the direction of entry of the sheet-like material, which narrows continuously in the direction of the wedge-shaped region delimited by the transfer median line between the impression cylinder and the preceding transfer cylinder. With the continuous narrowing of the nip width, the respective leading edge of the sheet-like material enters the storage device over as great a width as possible as far as the wedge-shaped region. The entry operation into the storage device, which takes place in the direction of rotation of the impression cylinder, is also assisted by the storage device, which is provided triangularly with a run-on slope in the wedge-shaped region of the two mutually cooperating cylinders. The previous sheet leading edge, now the new sheet trailing edge, runs up into the wedge-shaped region at the run-on slope, thus ensuring that the entire surface of the storage device, which faces the outer jacket surface of the impression cylinder, can be utilized as storage length.
Advantageously, the storage device may include, in an upper region thereof, but below the transfer median line between the impression cylinder and the preceding transfer cylinder, a retaining element which protects the sheet-like material entering the storage device against entry into the cylinder nip between the impression cylinder and the preceding transfer cylinder feeding the sheet-like material to the latter. The retaining element has provided therein, on the one hand, perforations in the manner of comb tines, which allow passage for gripper elements disposed on the outer jacket surface of the impression cylinder. Furthermore, at least one coating, for example of rubber or of other resilient materials, which damp the entry of the sheet-like material into the storage device, may be provided on the retaining element. In addition to the use of rubber or other elastic materials, the retaining element may have provided thereon an encapsulated damping gel, the consistency of which to a very great extent determines the damping behavior. The retaining element is preferably constructed so that it is provided, at the upper end thereof facing towards the transfer median line between the impression cylinder and the preceding transfer cylinder, with a hook-shaped over-engaging or overlapping portion which ensures that the sheet-like material which has entered the storage device does not project into the printing nip between the impression cylinder and the preceding transfer cylinder and is not gripped thereby.
According to a further realization of this concept upon which the invention is based, the impression cylinder may be provided with ejector elements for causing the sheet-like material to be ejected into the retaining device engaging over or overlapping the end of the sheet-like material which is in the form of extendable pins or blast nozzles which are activatable preferably in a cyclic manner and are activated whenever the sheet-like material has as far as possible entered the cylinder wedge of the impression cylinder and the preceding transfer cylinder.
In another realization of the concept upon which the invention is based, a deformation maximizing the storable length can be imparted to the sheet-like material by free jets acting contactlessly on that side of the sheet-like material which is yet to be printed.
During the entry of the sheet-like material into the storage device configured in accordance with the invention, the material is fixed at one edge by gripping devices of the following transfer cylinder, i.e., the turning or reversing drum. The gripping devices may be constructed as tongs grippers pivotable about the axis thereof. In an alternative version of the idea upon which the invention is based, by gripping devices arranged pivotably about the axis thereof in the following transfer cylinder, a bending moment causing deformation can be introduced to the sheet-like material entering the storage device into the continuously narrowing nip between the outer surface and the curved storage length.
In an alternative embodiment of the idea upon which the invention is based, the gripping devices which have gripped a sheet edge of the sheet-like material to be turned or reversed, execute, on the transfer cylinder functioning as a turning drum and following the impression cylinder, a yielding movement retreating behind the path of a sheet edge. The yielding movement of the gripper path on the transfer cylinder functioning as a turning drum and following the impression cylinder results, during the rotation of the turning drum and the impression cylinder, in a change in distance between the instantaneous gripper position and the outer jacket surface during the rotation of the two cylinders.
The storage device proposed according to the invention can be used particularly and preferably in the case of rotary printing machines processing relatively flexurally rigid material, such as for example, cardboard or pasteboard. In addition to relatively flexurally rigid materials, standard print carriers, such as, for example, papers of heavier or lighter grammage, can also be turned or reversed without difficulty. Turning or reversing devices, to which the storage device configured according to the invention may be assigned, are used preferably on multicolor rotary printing machines which process sheet-like material.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a turning or reversing device with a storage device for flat sheet-like material, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: